1. Field of the Invention
The present invention relates generally to a method and apparatus in mobile communications, and in particular to a communications network and the interaction of mobile user equipment (UE) with the network in accordance with interaction information.
2. Description of the Related Art
The relevant Third Generation Partnership Project (3GPP) Technical Specification Group (TSG) Working Groups (WGs) of System Archtecture Working Group 2 (SA2), Radio Access Network 2 (RAN2) and CT1 have agreed that the UE will be provided with a list of Tracking Areas (TAs) when that UE registers (or updates its registration) to the Enhanced Packet System (EPS). This list of TAs termed Multi-TAs (multiple TAs) will indicate to the UE that so long as the UE moves within the TAs given in the Multi-TA list, the UE need only perform a periodic TA update procedure to remain registered to the EPS. This concept is described in 3GPP TS 23.401.
A consensus is being reached in regards to RAN2 and CT1 that the realization of the Home E-Universal Terrestrial Radio Access Network (E-UTRAN) Node B (home eNB) feature and the campus NB feature should be done through the use of a “White list” of “allowed” TAs on which the UE could be listed. The background to the home eNB and campus NB concepts and their intended deployment scenarios are discussed in 3GPP documents C1-071667, C1-071668, with C1-071669 providing discussion on the workings of the White-TA list.
From TS 23.401 and TR 24.801 it is clear that managing the mobility of the UE will be facilitated by introducing to the UE a list of TAs that is understood by the UE to be the list of TAs in which the UE is registered and can obtain service in. So long as the UE moves within the TAs identified in this list of TAs, the UE need not update the Enhanced Packet Core (EPC) of its new location, other than having to perform periodic updates. This list of TA will be updated when the UE moves out to another TA that is not indicated on the list of TAs. This list of TAs allows for extended mobility in all the TAs of that list is termed the Multi-TA list.
Additionally, the 3GPP TSG WGs of RAN2 and CT1 are concluding that to solve the requirements of the home eNB and campus NB scenarios, the UE shall be given the identities of the TAs the UE can access if the UE wants services on these home eNBs (ie. Base Stations of the Long Term Evolution (LTE) system) and/or campus/business establishments NBs. Specifically, a list of TAs will be identified as TAs on which the UE may camp and receive service related to these home eNBs and/or campus/business establishments NBs. Since this list is not a list of TAs on which the UE is forbidden to camp, but rather, is a positive indication of TAs on which the UE may camp, this list of TAs is termed the White-TA list.
Accordingly, since the goal is to provide the UE with a Multi-TA list and also a White-TA list, work must take place to determine, for example, how these TA lists should be structured, how many TAs should be in each of these TA lists, and what signalling protocol messages will transport these TA lists.
To better understand the extent of the problems in the prior art, and in particular the problem of how many TAs are to be in the TA lists, the White-TA list will now be analyzed. As discussed in C1-071668, it is envisaged that home eNB deployment will be in the millions and campus deployment will be in hundreds of thousands.
While it is unlikely that any individual home owner will possess and run more than half a dozen home eNBs, it is likely that hotel premises or commercial businesses will have campus deployments with perhaps hundreds of eNBs. It may be unrealistic to provide to the UE a list with hundreds of entries of TA identities, because the list will be too extensive, resulting in transmission delay, inefficiencies and difficulty in management and maintainenance of both the UE and the EPC.
The same problem applies to the Multi-TA list. When the UE is in a TA that is identified in the Multi-TA list, it does not need to perform a Tracking Area Update (TAU) procedure. Accordingly, the larger the Multi-TA list the bigger the physical area in which the UE can move without performing TAU (except a periodic TAU if in IDLE). Considering that LTE cells will not be very large, it is believed that the size of a TA will not likely be the size of a Location Area (LA) but more like size of a Routing Area (RA) even if a TA identity can be shared by more than one LTE cell.
This belief is also based on the need for a Multi-TA to solve the problem of excessive TAU from UEs as can occur with frequent Routing Area Update (RAU) in General Packet Radio Service (GPRS) and Universal Mobile Telecommunications System (UMTS). If a given TA identity is common only between a small number of LTE cells, and there is a very large number of total LTE cells, in order to use Multi-TA efficiently the Multi-TA list should contain not just a few TAs, but instead should have upwards of dozens of TAs. The signalling message that carries this Multi-TA list has the potential to get very large.
It is believed in the specification work groups that each eNB will have a unique TA.
Exacerbating the problems, there will be more than one TA list—namely a Multi-TA list and a White-TA list—that have to be conveyed from the EPC to the UE. Additional lists may be conveyed to the UE as well. For example, suggestions have been made to provide a forbidden-TA list. Moreover, there is the already existing list of equivalent Public Land Mobile Networks (ePLMNs) that also has to be provided in those same Non-Access Stratum (NAS) signalling messages.
To further compound the problem, if the number of TAs for Multi-TA and or White-TA lists is fixed, then there could be no use cases of radio planning and new deployment scenarios where much more or fewer LTE cells or TAs need be provisioned to different parts of the network. That is to say, a fixed number of TAs might not fit all network operational situations.
Presently, there are no known solutions to these problems in the prior art. For example, in 3GPP TR 24.801, version 0.3.0 it is acknowledged that the maximum number of tracking areas which can be allocated per UE needs to be defined.
With regard to the number of ePLMNs that a Core Network (CN) conveys to a UE, and the prior art transport mechanisms, current 3GPP TR 24.008 provides a list of ePLMNs through LOCATION_UPDATING_ACCEPT, ATTACH_ACCEPT and ROUTING_AREA_UPDATE_ACCEPT. The number of ePLMNs that can be provided in the list of ePLMN is a maximum of 15 entries, although fewer can be provided. In 3GPP TR 23.401 and expanded in C1-071879, it is discussed that the TA list can be provided in the System Architecture Evolution (SAE) equivalent of the Temporary Mobile Subscriber Identity (TMSI) reallocation procedure (ie. the S-TMSI Reallocation procedure) adapting the TMSI REALLOCATION COMMAND message. However, neither 3GPP TR 24.401 nor C1-071879 provides any insight on the coding of the intended TA list or the size of that TA list.